It is important in metering dispensers of this class for the two chambers, in which the media to be dispensed in a metered manner are contained, to have a cross-sectional shape which promotes the tight contact of the follower piston with the entire circumference of the inner surface.
The storage chambers are therefore designed as cylindrical chambers in the prior-art two-chamber metering dispensers of this type (DE 41 20 644 C1, DE 42 12 413 C2, U.S. Pat. No. 4,949,874 and U.S. Pat. No. 4,438,871), and the storage chambers according to DE 42 12 413 and DE 41 20 644 can be inserted in the form of separate containers into a receiving housing, whose head is provided with a two-medium metering pump or with two metering pumps each associated with one container, which can be actuated by a common actuating member.
The other two documents mentioned pertain to two-chamber metering dispensers, in which the cylindrical storage chambers are arranged concentrically one inside the other, wherein the follower piston of the larger storage chamber is sealingly in contact with both the cylindrical inner surface of the circumferential wall and with the cylindrical outer surface of the smaller storage chamber.
The concentric arrangement of the two storage chambers has the drawback that both cannot have the same cross-sectional shape. The side-by-side arrangement of the two cylindrical storage chambers is disadvantageous because there are relatively large unused spaces between the pump housing, which accommodates the two storage containers and preferably has an elongated round shape, and the two cylindrical storage containers, these unused spaces being located between the mutually parallel side walls and the curvatures of the storage containers.
It has also been known that single metering dispensers can be provided with a storage chamber having an at least approximately elliptical cross-sectional shape. Such a cross-sectional shape of the storage chamber is preferred not only because of its optical appearance, but also because it better fits the hand and thus offers advantages in terms of handling. However, two-chamber metering dispensers with an elliptical shape are not known.
If two cylindrical storage chambers were inserted into such an elliptical housing shape, the unused space would be even larger than in the prior-art two-chamber metering dispensers with an elongated round housing shape.